Cyberknife stereotactic radiosurgery for the re-irradiation of brain lesions: a single-centre experience.

PURPOSE: The aim of our study was to retrospectively evaluate the feasibility and clinical benefit of cyberknife stereotactic radiosurgery (CSRS) in patients treated at Florence University for recurrent, pre-irradiated brain lesions. MATERIALS AND METHODS: Thirteen patients were retreated with cyberknife. Mean age was 47.1 years (range 33-77 years). Karnofsky performance status ranged from 60 to 100 (median 80). Eleven (84.6%) out of 13 patients had metastatic lesions: four (36.4%) had primary lung, three (27.2%) had primary breast cancer and four (36.4%) other types of solid malignancies. Two (15.4%) out of 13 patients had recurrent of glioblastoma. RESULTS: In terms of compliance with CSRS, the majority of patients did not develop any acute side effects. However, two (15.4%) out of 13 patients developed acute grade 2 toxicity requiring an increase of steroid medication. At the time of the last follow-up, response rates were as follows: complete response in one case (16.6%), partial response in three (50%) and stable disease in two (33.4%). CONCLUSIONS: Re-irradiation with CSRS is a feasible and effective option for pre-irradiated, recurrent brain lesions to obtain clinical benefit without excessive acute toxicity.

Salvage stereotactic re-irradiation with CyberKnife for locally recurrent head and neck cancer: a single center experience.

AIMS AND BACKGROUND: We report the toxicity and preliminary clinical outcome in patients affected by locally recurrent head and neck cancer treated with stereotactic re-irradiation. METHODS: Between February 2012 and August 2013, 17 patients were treated with CyberKnife as stereotactic re-irradiation for locally recurrent head and neck cancer. All patients had previously received a full dose radiation treatment with radical intent, with a median total dose of 66 Gy (range, 50-70) delivered with standard fractionation. The median interval between the primary radiotherapy and re-irradiation was 24 months (range, 10-168). RESULTS: All patients completed the prescribed treatment, which was delivered in 5 fractions. The median tumor dose administered was 30 Gy (range, 25-35) prescribed to the 80% isodose line. Treatment sites were as follows: neck lymph nodes in 5 patients, paranasal sinuses in 5, oropharynx in 2, nasopharynx, and larynx, oral cavity, nasal fossa and parotid gland each in 1 patient. The median target volume treated was 58.7 cm3 (range, 8.5-211.3). Sixteen patients (94%) were evaluated for response. At a median follow-up of 7.5 months (range, 2-17), 4 patients achieved complete response (25%), 5 had partial response (31%) and 7 showed stable disease (44%). No patient showed in-field progression after re-irradiation. Grade 3 acute toxicity was noted in one patient only; no late side effect was observed during the follow-up. CONCLUSIONS: Stereotactic re-irradiation with CyberKnife is an appealing non-surgical salvage treatment for selected patients with local-regionally recurrent head and neck cancer.

Impact of plan parameters on the dosimetric accuracy of volumetric modulated arc therapy.

PURPOSE: To evaluate the effect of plan parameters on volumetric modulated arc therapy (VMAT) dosimetric accuracy, together with the possibility of scoring plan complexity. METHODS: 142 clinical VMAT plans initially optimized using a 4° control point (CP) separation were evaluated. All plans were delivered by a 6 MV Linac to a biplanar diode array for patient-specific quality assurance (QA). Local Γ index analysis (3%, 3 mm and 2%, 2 mm) enabled the comparison between delivered and calculated dose. The following parameters were considered for each plan: average leaf travel (LT), modulation complexity score applied to VMAT (MCSv), MU value, and a multiplicative combination of LT and MCSv (LTMCS). Pearson's correlation analysis was performed between Γ passing rates and each parameter. The effects of CP angular separation on VMAT dosimetric accuracy were also analyzed by focusing on plans with high LT values. Forty out of 142 plans with LT above 350 mm were further optimized using a finer angle spacing (3° or 2°) and Γ analysis was performed. The average Γ passing rates obtained at 4° and at 3°∕2° sampling were compared. A further correlation analysis between all parameters and the Γ pass-rates was performed on 142 plans, but including the newly optimized 40 plans (CP every 3° or 2°) in place of the old ones (CP every 4°). RESULTS: A moderate significant (p < 0.05) correlation between each examined parameter and Γ passing rates was observed for the original 142 plans at 4° CP discretization. A negative correlation was found for LT with Pearson's r absolute values above 0.6, suggesting that a lower dosimetric accuracy may be expected for higher LT values when a 4° CP sampling is used. A positive correlation was observed for MCSv and LTMCS with r values above 0.5. In order to score plan complexity, threshold values of LTMCS were defined. The average Γ passing rates were significantly higher for the plans created using the finer CP spacing (3°∕2°) compared to the plans optimized using the standard 4° spacing (Student t-test p < 0.05). The correlation between LT and passing rates was strongly diminished when plans with finer angular separations were considered, yielding Pearson's r absolute values below 0.45. CONCLUSIONS: At 4° CP sampling, LT, MCSv, and LTMCS were found to be significantly correlated with VMAT dosimetric accuracy, expressed as Γ pass-rates. These parameters were found to be possible candidates for scoring plan complexity using threshold values. A finer CP separation (3°∕2°) led to a significant increase in dosimetric accuracy for plans with high leaf travel values, and to a decrease in correlation between LT and Γ passing rates. These results indicated that the influence of LT on VMAT dosimetric accuracy can be controlled by reducing CP separation. CP spacing for all plans requiring large leaf motion should not exceed 3°. The reported data were integrated to optimize our clinical workflow for plan creation, optimization, selection among rival plans, and patient-specific QA of VMAT treatments.